Checking more JS API return values for failure.

"max_bytes" value is insufficient for the number of configured items:
by defining dynamically created objects and arrays as properties of child
objects of the global object immediately after such objects are created,
they are "implicitly rooted", protecting them from (unexpected) garbage
collection. Now the initialization will simply fail with a nice "out of memory"
error. This was a long-standing bug that rarely occurred in the wild.

Fixed is_operator property (was always true).
Created is_download_free() function which checks all the various criteria that
can make a download free for a particular user from a particular file area,
with support for per-directory exemption ARS (finally).

Added more property descriptions (for dynamic JS object model docs).
Fixed a few bugs exposed by jsdocs.js.
Using JS_NewNumberValue for full 32-bit integer support (bitfields mostly).

reasignment by script author accidentally using object name as local variable.

user has access to in a single object (associative array).

to scripts with no user logged in (e.g. fingerservice.js).

upload_dir.

will be undefined.

max_files, max_age, upload_credit_pct, and download_credit_pct.

and is_operator.